Computerized mass detection in whole breast ultrasound images: Reduction of false positives using bilateral subtraction technique Yuji Ikedo a , Daisuke Fukuoka b , Takeshi Hara a , Hiroshi Fujita a , Etsuo Takada c , Tokiko Endo d , and Takako Morita e a Department of Intelligent Image Information, Division of Regeneration and Advanced Medical Sciences, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu 501-1194, JAPAN; b Technology Education, Faculty of Education, Gifu University, 1-1 Yanagido, Gifu 501-1193, JAPAN; c Division of Medical Ultrasonics, Center of Optical Medicine, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Tochigi 321-0293, JAPAN; d Department of Radiology, National Hospital Organization Nagoya Medical Center, 4-1-1 Sannomaru, Naka-ku, Naogya, Aichi 460-0001, JAPAN; e Department of Mammary Gland, Chunichi Hospital, 3-6-38 Marunouchi, Naka-ku, Nagoya, Aichi 460-0002, JAPAN ABSTRACT The comparison of left and right mammograms is a common technique used by radiologists for the detection and diagnosis of masses. In mammography, computer-aided detection (CAD) schemes using bilateral subtraction technique have been reported. However, in breast ultrasonography, there are no reports on CAD schemes using comparison of left and right breasts. In this study, we propose a scheme of false positive reduction based on bilateral subtraction technique in whole breast ultrasound images. Mass candidate regions are detected by using the information of edge directions. Bilateral breast images are registered with reference to the nipple positions and skin lines. A false positive region is detected based on a comparison of the average gray values of a mass candidate region and a region with the same position and same size as the candidate region in the contralateral breast. In evaluating the effectiveness of the false positive reduction method, three normal and three abnormal bilateral pairs of whole breast images were employed. These abnormal breasts included six masses larger than 5 mm in diameter. The sensitivity was 83% (5/6) with 13.8 (165/12) false positives per breast before applying the proposed reduction method. By applying the method, false positives were reduced to 4.5 (54/12) per breast without removing a true positive region. This preliminary study indicates that the bilateral subtraction technique is effective for improving the performance of a CAD scheme in whole breast ultrasound images. Keywords: whole breast ultrasound image, computer-aided detection, bilateral subtraction 1. INTRODUCTION Breast cancer has had the highest incident rate among all women’s cancer since 1996 in Japan. Therefore, the detection and treatment of breast masses at an early stage of breast masses are important tasks for radiologists and surgeons. Currently, mammography and ultrasonography are used as reliable methods for early detection of masses in breast cancer screening. Screening using mammography has been established for women over 40 years of age with the recommendation of the government in Japan. However, it has been reported that screening using mammography together with ultrasonography is effective in the detection of breast cancer. 1–3 It response to that finding, the Japanese government decided to investigate the effectiveness of the combination screening corresponding author email: ikedo@fjt.info.gifu-u.ac.jp Honorable Mention Poster Award Medical Imaging 2007: Computer-Aided Diagnosis, edited by Maryellen L. Giger, Nico Karssemeijer, Proc. of SPIE Vol. 6514, 65141T, (2007) · 1605-7422/07/$18 · doi: 10.1117/12.709225 Proc. of SPIE Vol. 6514 65141T-1